[SCSI] qla2xxx: Reduce mbx-command timeout for Login/Logout requests.

Don't use default 30 second mailbox-command timeout for these
serial requests, instead, limit the TMO to the standard 2*RATOV
plus some fudge-factor.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>